A motley collection of ideas
Homemade circuits, experiments, tinker-friendly electronic ideas, and and things related to amateur radio.
In 1983, Rádiótechnika magazine published an article about a clock built around the TMS1122 IC. I redesigned the circuit and the PCB somewhat, then built it. It served continuously for 27 years, essentially without being turned off. Due to lack of space, I recently scrapped it, though it was still in working condition. The Clock … Read more
Fluorescent lamps are becoming less and less fashionable these days, as LEDs are pushing them out—but they’re really not that bad. The technology improved a lot between the 1970s and 1990s: the unpleasant light of old fluorescent tubes is a thing of the past. Flickering and color distortion have been reduced so effectively that in … Read more
I inherited this device from my father—he brought it from the Soviet Union at some point. It was manufactured in 1974 and is a typical example of the simple yet extremely robust Soviet devices. It doesn’t contain any “smart” electronic circuits, so there’s nothing in it that could burn out or break. It’s simply built … Read more
Spotters, SWL (shortwave listening) enthusiasts, and amateur radio operators all enjoy listening to aircraft communications — and nowadays, even drone pilots find it useful to monitor air traffic. A good handheld airband transceiver easily costs well over a hundred thousand forints, whereas the device described here is dirt cheap by comparison. Of course, it’s not … Read more
The handheld meter has been a staple in almost every technician’s toolkit for nearly 100 years. Today, the majority of handheld meters have digital displays. However, until the 1970s, most meters featured analog readouts. These were typically multimeters capable of measuring voltage, current, resistance, and occasionally capacitance and frequency. “Pocket watch”-style measuring instruments were popular … Read more
The purpose of this project is to extend the range of an older (and more affordable) frequency counter into the VHF and UHF bands. The idea was inspired by an article published in Rádiótechnika (1990/7, pp. 341–342), although the original circuit was designed by Zeljko Bozic, S52ZB, and later published in a 2006 issue of … Read more
Sometimes I find myself wondering which of my portable digital voltmeters I can actually trust. The old 4½-digit M4650? The Fulke? Or the younger METEX? (Okay, I have one from Lidl too, but that’s not even a question.) Generally, they all show pretty similar values, and I rarely need better than 1–2% accuracy—but it still … Read more
I needed a compact power supply capable of providing roughly 5–20 V DC and 12–16 V AC. Because an AC output was required, I chose a conventional transformer—similar to those used in alarm control units and intercom systems. This project was inspired by the Chordless Lab Power Supply on Thingiverse. DC Section The DC side is quite simple: a … Read more
The phenomenon of resonance has many examples in physics, engineering, and everyday life, and the reed frequency meter is one of them. Surprisingly, such instruments are still in use here and there, although they are certainly considered rarities today. I picked up this specimen, manufactured in 1961, for a few coins at a swap meet. … Read more
My better half has a weakness for weather stations, and she especially likes this old piece. It’s not particularly smart, not particularly pretty, but it has a “frog”, which makes up for everything. It’s a cheap LIDL model — even the first one we bought didn’t pick up the signal from the external sensor. They replaced … Read more